Our invention is directed to a prosthetic mechanical heart valve with an improved stiffening ring, and in particular a stiffening ring which is compressible with respect to an annular body of the valve, whereby a satisfactory margin of safety is obtained despite a relatively thinner valve body and ring combination. This feature, coupled with beveled stops for valve leaflets, permits spring-loading of the leaflets, by deformation of the annular valve body.
Heart valve prostheses may be classified into two general categories: bioprosthetic heart valves and mechanical heart valves. By bioprosthetic heart valves we mean heart valves with generally flexible leaflets comprised of biological tissue. These include leaflets formed of treated human valve tissue (allografts), or of treated porcine or other non-human tissue (xenografts). By mechanical heart valves we mean heart valves comprised primarily of non-biologic materials, for example, metals, ceramics or polymers. These include ball valves and valves having one, two or more leaflets.
An implantable mechanical heart valve usually has an annular valve housing or body to provide a passageway for blood. Leaflets are mounted in the annular body and open or close the passageway. Usually there are one or two leaflets, but occasionally triple leaflet configurations have been proposed. On the outside of the valve body there is usually a circumferential groove. This groove is used to attach a suture ring to the valve body. The suture ring is used to sew the heart valve to the patient's heart tissue. A stiffening ring has been used with some sewing rings to give additional strength to the valve body. Generally, the stiffening ring has been designed to be in intimate contact with an outer surface of the valve body. An exception has been the CPHV (.TM.) heart valve made by Carbomedics, Inc., our assignee. Because this valve has been designed with a rotatable sewing ring, there has usually been a small gap of not more than 0.001 inch (0.025 mm) radially between the valve body and the stiffening ring. This has not, however, permitted a significant reduction in the radial thickness of the valve body and stiffening ring/sewing ring combination with associated increase in orifice size.